diff --git a/src/source/JNIGenerator.scala b/src/source/JNIGenerator.scala
index 971657dcf..0492ad36b 100644
--- a/src/source/JNIGenerator.scala
+++ b/src/source/JNIGenerator.scala
@@ -173,7 +173,7 @@ class JNIGenerator(spec: Spec) extends Generator(spec) {
           w.wl(s"const auto& data = ::djinni::JniClass<$jniHelper>::get();")
         writeAlignedCall(w, "return {", r.fields, "}", f => {
           val fieldId = "data.field_" + idJava.field(f.ident)
-          val jniFieldAccess = toJniCall(f.ty, (jt: String) => s"jniEnv->Get${jt}Field(j, $fieldId)")
+          val jniFieldAccess = toJniCall(f.ty, (jt: String) => s"jniEnv->Get${jt}Field(j, $fieldId)") + ")"
           jniMarshal.toCpp(f.ty, jniFieldAccess)
         })
         w.wl(";")
@@ -298,7 +298,9 @@ class JNIGenerator(spec: Spec) extends Generator(spec) {
             }
             else
               w.w(")")
-            w.wl(";")
+            if (m.ret.nonEmpty)
+              w.w(")");
+            w.wl(";");
             w.wl(s"::djinni::jniExceptionCheck(jniEnv);")
             m.ret.fold()(ty => {
               (spec.cppNnCheckExpression, isInterface(ty.resolved)) match {
@@ -404,11 +406,11 @@ class JNIGenerator(spec: Spec) extends Generator(spec) {
 
   def toJniCall(ty: TypeRef, f: String => String): String = toJniCall(ty.resolved, f, false)
   def toJniCall(m: MExpr, f: String => String, needRef: Boolean): String = m.base match {
-    case p: MPrimitive => f(if (needRef) "Object" else IdentStyle.camelUpper(p.jName))
-    case MString => "(jstring)" + f("Object")
+    case p: MPrimitive => "(" + f(if (needRef) "Object" else IdentStyle.camelUpper(p.jName))
+    case MString => "reinterpret_cast<jstring>(" + f("Object")
     case MOptional => toJniCall(m.args.head, f, true)
-    case MBinary => "(jbyteArray)" + f("Object")
-    case _ => f("Object")
+    case MBinary => "reinterpret_cast<jbyteArray>(" + f("Object")
+    case _ => "(" + f("Object")
   }
 
   def cppTypeArgs(params: Seq[TypeParam]): String =
diff --git a/support-lib/objc/DJIMarshal+Private.h b/support-lib/objc/DJIMarshal+Private.h
index f0ff9d9a5..bb21fc28e 100644
--- a/support-lib/objc/DJIMarshal+Private.h
+++ b/support-lib/objc/DJIMarshal+Private.h
@@ -165,7 +165,7 @@ struct WString {
         assert(string);
         NSStringEncoding encoding = getWCharEncoding<sizeof(wchar_t)>();
         NSData* data = [string dataUsingEncoding:encoding];
-        return std::wstring((wchar_t*)[data bytes], [data length] / sizeof (wchar_t));
+        return std::wstring(reinterpret_cast<const wchar_t*>([data bytes]), [data length] / sizeof (wchar_t));
     }
 
     static ObjcType fromCpp(const CppType& string) {
diff --git a/test-suite/generated-src/jni/NativeAssortedPrimitives.cpp b/test-suite/generated-src/jni/NativeAssortedPrimitives.cpp
index 098a8a2fc..23d06915c 100644
--- a/test-suite/generated-src/jni/NativeAssortedPrimitives.cpp
+++ b/test-suite/generated-src/jni/NativeAssortedPrimitives.cpp
@@ -35,20 +35,20 @@ auto NativeAssortedPrimitives::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 15);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeAssortedPrimitives>::get();
-    return {::djinni::Bool::toCpp(jniEnv, jniEnv->GetBooleanField(j, data.field_mB)),
-            ::djinni::I8::toCpp(jniEnv, jniEnv->GetByteField(j, data.field_mEight)),
-            ::djinni::I16::toCpp(jniEnv, jniEnv->GetShortField(j, data.field_mSixteen)),
-            ::djinni::I32::toCpp(jniEnv, jniEnv->GetIntField(j, data.field_mThirtytwo)),
-            ::djinni::I64::toCpp(jniEnv, jniEnv->GetLongField(j, data.field_mSixtyfour)),
-            ::djinni::F32::toCpp(jniEnv, jniEnv->GetFloatField(j, data.field_mFthirtytwo)),
-            ::djinni::F64::toCpp(jniEnv, jniEnv->GetDoubleField(j, data.field_mFsixtyfour)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::Bool>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOB)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I8>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOEight)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I16>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOSixteen)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOThirtytwo)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOSixtyfour)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::F32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOFthirtytwo)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::F64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOFsixtyfour))};
+    return {::djinni::Bool::toCpp(jniEnv, (jniEnv->GetBooleanField(j, data.field_mB))),
+            ::djinni::I8::toCpp(jniEnv, (jniEnv->GetByteField(j, data.field_mEight))),
+            ::djinni::I16::toCpp(jniEnv, (jniEnv->GetShortField(j, data.field_mSixteen))),
+            ::djinni::I32::toCpp(jniEnv, (jniEnv->GetIntField(j, data.field_mThirtytwo))),
+            ::djinni::I64::toCpp(jniEnv, (jniEnv->GetLongField(j, data.field_mSixtyfour))),
+            ::djinni::F32::toCpp(jniEnv, (jniEnv->GetFloatField(j, data.field_mFthirtytwo))),
+            ::djinni::F64::toCpp(jniEnv, (jniEnv->GetDoubleField(j, data.field_mFsixtyfour))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::Bool>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOB))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I8>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOEight))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I16>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOSixteen))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOThirtytwo))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOSixtyfour))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::F32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOFthirtytwo))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::F64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOFsixtyfour)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeClientInterface.cpp b/test-suite/generated-src/jni/NativeClientInterface.cpp
index 16f9c9b5f..31df0c030 100644
--- a/test-suite/generated-src/jni/NativeClientInterface.cpp
+++ b/test-suite/generated-src/jni/NativeClientInterface.cpp
@@ -19,10 +19,10 @@ ::testsuite::ClientReturnedRecord NativeClientInterface::JavaProxy::get_record(i
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeClientInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_getRecord,
-                                         ::djinni::get(::djinni::I64::fromCpp(jniEnv, c_record_id)),
-                                         ::djinni::get(::djinni::String::fromCpp(jniEnv, c_utf8string)),
-                                         ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni::String>::fromCpp(jniEnv, c_misc)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_getRecord,
+                                          ::djinni::get(::djinni::I64::fromCpp(jniEnv, c_record_id)),
+                                          ::djinni::get(::djinni::String::fromCpp(jniEnv, c_utf8string)),
+                                          ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni::String>::fromCpp(jniEnv, c_misc))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni_generated::NativeClientReturnedRecord::toCpp(jniEnv, jret);
 }
@@ -30,10 +30,10 @@ double NativeClientInterface::JavaProxy::identifier_check(const std::vector<uint
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeClientInterface>::get();
-    auto jret = jniEnv->CallDoubleMethod(Handle::get().get(), data.method_identifierCheck,
-                                         ::djinni::get(::djinni::Binary::fromCpp(jniEnv, c_data)),
-                                         ::djinni::get(::djinni::I32::fromCpp(jniEnv, c_r)),
-                                         ::djinni::get(::djinni::I64::fromCpp(jniEnv, c_jret)));
+    auto jret = (jniEnv->CallDoubleMethod(Handle::get().get(), data.method_identifierCheck,
+                                          ::djinni::get(::djinni::Binary::fromCpp(jniEnv, c_data)),
+                                          ::djinni::get(::djinni::I32::fromCpp(jniEnv, c_r)),
+                                          ::djinni::get(::djinni::I64::fromCpp(jniEnv, c_jret))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::F64::toCpp(jniEnv, jret);
 }
@@ -41,7 +41,7 @@ std::string NativeClientInterface::JavaProxy::return_str() {
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeClientInterface>::get();
-    auto jret = (jstring)jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnStr);
+    auto jret = reinterpret_cast<jstring>(jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnStr));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::String::toCpp(jniEnv, jret);
 }
@@ -49,8 +49,8 @@ std::string NativeClientInterface::JavaProxy::meth_taking_interface(const std::s
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeClientInterface>::get();
-    auto jret = (jstring)jniEnv->CallObjectMethod(Handle::get().get(), data.method_methTakingInterface,
-                                                  ::djinni::get(::djinni_generated::NativeClientInterface::fromCpp(jniEnv, c_i)));
+    auto jret = reinterpret_cast<jstring>(jniEnv->CallObjectMethod(Handle::get().get(), data.method_methTakingInterface,
+                                                                   ::djinni::get(::djinni_generated::NativeClientInterface::fromCpp(jniEnv, c_i))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::String::toCpp(jniEnv, jret);
 }
@@ -58,8 +58,8 @@ std::string NativeClientInterface::JavaProxy::meth_taking_optional_interface(con
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeClientInterface>::get();
-    auto jret = (jstring)jniEnv->CallObjectMethod(Handle::get().get(), data.method_methTakingOptionalInterface,
-                                                  ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeClientInterface>::fromCpp(jniEnv, c_i)));
+    auto jret = reinterpret_cast<jstring>(jniEnv->CallObjectMethod(Handle::get().get(), data.method_methTakingOptionalInterface,
+                                                                   ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeClientInterface>::fromCpp(jniEnv, c_i))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::String::toCpp(jniEnv, jret);
 }
diff --git a/test-suite/generated-src/jni/NativeClientReturnedRecord.cpp b/test-suite/generated-src/jni/NativeClientReturnedRecord.cpp
index da59503ed..580247fc8 100644
--- a/test-suite/generated-src/jni/NativeClientReturnedRecord.cpp
+++ b/test-suite/generated-src/jni/NativeClientReturnedRecord.cpp
@@ -24,9 +24,9 @@ auto NativeClientReturnedRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 4);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeClientReturnedRecord>::get();
-    return {::djinni::I64::toCpp(jniEnv, jniEnv->GetLongField(j, data.field_mRecordId)),
-            ::djinni::String::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mContent)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::String>::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mMisc))};
+    return {::djinni::I64::toCpp(jniEnv, (jniEnv->GetLongField(j, data.field_mRecordId))),
+            ::djinni::String::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mContent))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::String>::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mMisc)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeConstantRecord.cpp b/test-suite/generated-src/jni/NativeConstantRecord.cpp
index 209246b71..36baf63e3 100644
--- a/test-suite/generated-src/jni/NativeConstantRecord.cpp
+++ b/test-suite/generated-src/jni/NativeConstantRecord.cpp
@@ -23,8 +23,8 @@ auto NativeConstantRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 3);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeConstantRecord>::get();
-    return {::djinni::I32::toCpp(jniEnv, jniEnv->GetIntField(j, data.field_mSomeInteger)),
-            ::djinni::String::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mSomeString))};
+    return {::djinni::I32::toCpp(jniEnv, (jniEnv->GetIntField(j, data.field_mSomeInteger))),
+            ::djinni::String::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mSomeString)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeDateRecord.cpp b/test-suite/generated-src/jni/NativeDateRecord.cpp
index b2580e16c..3d40b41ba 100644
--- a/test-suite/generated-src/jni/NativeDateRecord.cpp
+++ b/test-suite/generated-src/jni/NativeDateRecord.cpp
@@ -22,7 +22,7 @@ auto NativeDateRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeDateRecord>::get();
-    return {::djinni::Date::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mCreatedAt))};
+    return {::djinni::Date::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mCreatedAt)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeEnumUsageInterface.cpp b/test-suite/generated-src/jni/NativeEnumUsageInterface.cpp
index 4e84735d3..3ad92165e 100644
--- a/test-suite/generated-src/jni/NativeEnumUsageInterface.cpp
+++ b/test-suite/generated-src/jni/NativeEnumUsageInterface.cpp
@@ -19,8 +19,8 @@ ::testsuite::color NativeEnumUsageInterface::JavaProxy::e(::testsuite::color c_e
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeEnumUsageInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_e,
-                                         ::djinni::get(::djinni_generated::NativeColor::fromCpp(jniEnv, c_e)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_e,
+                                          ::djinni::get(::djinni_generated::NativeColor::fromCpp(jniEnv, c_e))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni_generated::NativeColor::toCpp(jniEnv, jret);
 }
@@ -28,8 +28,8 @@ std::experimental::optional<::testsuite::color> NativeEnumUsageInterface::JavaPr
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeEnumUsageInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_o,
-                                         ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeColor>::fromCpp(jniEnv, c_o)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_o,
+                                          ::djinni::get(::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeColor>::fromCpp(jniEnv, c_o))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeColor>::toCpp(jniEnv, jret);
 }
@@ -37,8 +37,8 @@ std::vector<::testsuite::color> NativeEnumUsageInterface::JavaProxy::l(const std
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeEnumUsageInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_l,
-                                         ::djinni::get(::djinni::List<::djinni_generated::NativeColor>::fromCpp(jniEnv, c_l)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_l,
+                                          ::djinni::get(::djinni::List<::djinni_generated::NativeColor>::fromCpp(jniEnv, c_l))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::List<::djinni_generated::NativeColor>::toCpp(jniEnv, jret);
 }
@@ -46,8 +46,8 @@ std::unordered_set<::testsuite::color> NativeEnumUsageInterface::JavaProxy::s(co
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeEnumUsageInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_s,
-                                         ::djinni::get(::djinni::Set<::djinni_generated::NativeColor>::fromCpp(jniEnv, c_s)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_s,
+                                          ::djinni::get(::djinni::Set<::djinni_generated::NativeColor>::fromCpp(jniEnv, c_s))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::Set<::djinni_generated::NativeColor>::toCpp(jniEnv, jret);
 }
@@ -55,8 +55,8 @@ std::unordered_map<::testsuite::color, ::testsuite::color> NativeEnumUsageInterf
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeEnumUsageInterface>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_m,
-                                         ::djinni::get(::djinni::Map<::djinni_generated::NativeColor, ::djinni_generated::NativeColor>::fromCpp(jniEnv, c_m)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_m,
+                                          ::djinni::get(::djinni::Map<::djinni_generated::NativeColor, ::djinni_generated::NativeColor>::fromCpp(jniEnv, c_m))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::Map<::djinni_generated::NativeColor, ::djinni_generated::NativeColor>::toCpp(jniEnv, jret);
 }
diff --git a/test-suite/generated-src/jni/NativeEnumUsageRecord.cpp b/test-suite/generated-src/jni/NativeEnumUsageRecord.cpp
index 0460969ac..1e58a771e 100644
--- a/test-suite/generated-src/jni/NativeEnumUsageRecord.cpp
+++ b/test-suite/generated-src/jni/NativeEnumUsageRecord.cpp
@@ -27,11 +27,11 @@ auto NativeEnumUsageRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 6);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeEnumUsageRecord>::get();
-    return {::djinni_generated::NativeColor::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mE)),
-            ::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeColor>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mO)),
-            ::djinni::List<::djinni_generated::NativeColor>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mL)),
-            ::djinni::Set<::djinni_generated::NativeColor>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mS)),
-            ::djinni::Map<::djinni_generated::NativeColor, ::djinni_generated::NativeColor>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mM))};
+    return {::djinni_generated::NativeColor::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mE))),
+            ::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeColor>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mO))),
+            ::djinni::List<::djinni_generated::NativeColor>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mL))),
+            ::djinni::Set<::djinni_generated::NativeColor>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mS))),
+            ::djinni::Map<::djinni_generated::NativeColor, ::djinni_generated::NativeColor>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mM)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeExtendedRecord.cpp b/test-suite/generated-src/jni/NativeExtendedRecord.cpp
index 57ebe529b..2240f6a33 100644
--- a/test-suite/generated-src/jni/NativeExtendedRecord.cpp
+++ b/test-suite/generated-src/jni/NativeExtendedRecord.cpp
@@ -22,7 +22,7 @@ auto NativeExtendedRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeExtendedRecord>::get();
-    return {::djinni::Bool::toCpp(jniEnv, jniEnv->GetBooleanField(j, data.field_mFoo))};
+    return {::djinni::Bool::toCpp(jniEnv, (jniEnv->GetBooleanField(j, data.field_mFoo)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeExternInterface2.cpp b/test-suite/generated-src/jni/NativeExternInterface2.cpp
index a61b1d101..1bab65028 100644
--- a/test-suite/generated-src/jni/NativeExternInterface2.cpp
+++ b/test-suite/generated-src/jni/NativeExternInterface2.cpp
@@ -19,8 +19,8 @@ ::ExternRecordWithDerivings NativeExternInterface2::JavaProxy::foo(const std::sh
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeExternInterface2>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_foo,
-                                         ::djinni::get(::djinni_generated::NativeTestHelpers::fromCpp(jniEnv, c_i)));
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_foo,
+                                          ::djinni::get(::djinni_generated::NativeTestHelpers::fromCpp(jniEnv, c_i))));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni_generated::NativeExternRecordWithDerivings::toCpp(jniEnv, jret);
 }
diff --git a/test-suite/generated-src/jni/NativeExternRecordWithDerivings.cpp b/test-suite/generated-src/jni/NativeExternRecordWithDerivings.cpp
index 994cc64f2..233f22e5d 100644
--- a/test-suite/generated-src/jni/NativeExternRecordWithDerivings.cpp
+++ b/test-suite/generated-src/jni/NativeExternRecordWithDerivings.cpp
@@ -24,8 +24,8 @@ auto NativeExternRecordWithDerivings::toCpp(JNIEnv* jniEnv, JniType j) -> CppTyp
     ::djinni::JniLocalScope jscope(jniEnv, 3);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeExternRecordWithDerivings>::get();
-    return {::djinni_generated::NativeRecordWithDerivings::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mMember)),
-            ::djinni_generated::NativeColor::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mE))};
+    return {::djinni_generated::NativeRecordWithDerivings::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mMember))),
+            ::djinni_generated::NativeColor::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mE)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeMapDateRecord.cpp b/test-suite/generated-src/jni/NativeMapDateRecord.cpp
index eb359d1ee..6cf61193c 100644
--- a/test-suite/generated-src/jni/NativeMapDateRecord.cpp
+++ b/test-suite/generated-src/jni/NativeMapDateRecord.cpp
@@ -22,7 +22,7 @@ auto NativeMapDateRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeMapDateRecord>::get();
-    return {::djinni::Map<::djinni::String, ::djinni::Date>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mDatesById))};
+    return {::djinni::Map<::djinni::String, ::djinni::Date>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mDatesById)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeMapListRecord.cpp b/test-suite/generated-src/jni/NativeMapListRecord.cpp
index a29ae6fdd..ef11b90d9 100644
--- a/test-suite/generated-src/jni/NativeMapListRecord.cpp
+++ b/test-suite/generated-src/jni/NativeMapListRecord.cpp
@@ -22,7 +22,7 @@ auto NativeMapListRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeMapListRecord>::get();
-    return {::djinni::List<::djinni::Map<::djinni::String, ::djinni::I64>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mMapList))};
+    return {::djinni::List<::djinni::Map<::djinni::String, ::djinni::I64>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mMapList)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeMapRecord.cpp b/test-suite/generated-src/jni/NativeMapRecord.cpp
index 21dd19245..f0368aebf 100644
--- a/test-suite/generated-src/jni/NativeMapRecord.cpp
+++ b/test-suite/generated-src/jni/NativeMapRecord.cpp
@@ -23,8 +23,8 @@ auto NativeMapRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 3);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeMapRecord>::get();
-    return {::djinni::Map<::djinni::String, ::djinni::I64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mMap)),
-            ::djinni::Map<::djinni::I32, ::djinni::I32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mImap))};
+    return {::djinni::Map<::djinni::String, ::djinni::I64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mMap))),
+            ::djinni::Map<::djinni::I32, ::djinni::I32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mImap)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeNestedCollection.cpp b/test-suite/generated-src/jni/NativeNestedCollection.cpp
index 2d4333095..ddb70525e 100644
--- a/test-suite/generated-src/jni/NativeNestedCollection.cpp
+++ b/test-suite/generated-src/jni/NativeNestedCollection.cpp
@@ -22,7 +22,7 @@ auto NativeNestedCollection::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeNestedCollection>::get();
-    return {::djinni::List<::djinni::Set<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mSetList))};
+    return {::djinni::List<::djinni::Set<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mSetList)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableList.cpp b/test-suite/generated-src/jni/NativeParcelableList.cpp
index ae13be082..b51d6a4e8 100644
--- a/test-suite/generated-src/jni/NativeParcelableList.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableList.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableList::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableList>::get();
-    return {::djinni::List<::djinni::String>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mL))};
+    return {::djinni::List<::djinni::String>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mL)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableListMapSet.cpp b/test-suite/generated-src/jni/NativeParcelableListMapSet.cpp
index 3e75d27f2..f8fbafa35 100644
--- a/test-suite/generated-src/jni/NativeParcelableListMapSet.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableListMapSet.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableListMapSet::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableListMapSet>::get();
-    return {::djinni::List<::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mListMapSet))};
+    return {::djinni::List<::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mListMapSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableListSet.cpp b/test-suite/generated-src/jni/NativeParcelableListSet.cpp
index 0ca617a92..3a95a9c84 100644
--- a/test-suite/generated-src/jni/NativeParcelableListSet.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableListSet.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableListSet::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableListSet>::get();
-    return {::djinni::List<::djinni::Set<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mListSet))};
+    return {::djinni::List<::djinni::Set<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mListSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableMap.cpp b/test-suite/generated-src/jni/NativeParcelableMap.cpp
index 3ba1b6e3e..20584c764 100644
--- a/test-suite/generated-src/jni/NativeParcelableMap.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableMap.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableMap::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableMap>::get();
-    return {::djinni::Map<::djinni::String, ::djinni::String>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mM))};
+    return {::djinni::Map<::djinni::String, ::djinni::String>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mM)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableMapList.cpp b/test-suite/generated-src/jni/NativeParcelableMapList.cpp
index d14333fae..6ca835619 100644
--- a/test-suite/generated-src/jni/NativeParcelableMapList.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableMapList.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableMapList::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableMapList>::get();
-    return {::djinni::Map<::djinni::String, ::djinni::List<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mMapSet))};
+    return {::djinni::Map<::djinni::String, ::djinni::List<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mMapSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableMapSet.cpp b/test-suite/generated-src/jni/NativeParcelableMapSet.cpp
index afb2b5a33..2ad87a768 100644
--- a/test-suite/generated-src/jni/NativeParcelableMapSet.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableMapSet.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableMapSet::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableMapSet>::get();
-    return {::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mMapSet))};
+    return {::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mMapSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableOptionalList.cpp b/test-suite/generated-src/jni/NativeParcelableOptionalList.cpp
index 62a4a29ca..9c70717f6 100644
--- a/test-suite/generated-src/jni/NativeParcelableOptionalList.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableOptionalList.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableOptionalList::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableOptionalList>::get();
-    return {::djinni::Optional<std::experimental::optional, ::djinni::List<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOptionalSet))};
+    return {::djinni::Optional<std::experimental::optional, ::djinni::List<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOptionalSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableOptionalMap.cpp b/test-suite/generated-src/jni/NativeParcelableOptionalMap.cpp
index 4816639f1..d93d37607 100644
--- a/test-suite/generated-src/jni/NativeParcelableOptionalMap.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableOptionalMap.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableOptionalMap::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableOptionalMap>::get();
-    return {::djinni::Optional<std::experimental::optional, ::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOptionalSet))};
+    return {::djinni::Optional<std::experimental::optional, ::djinni::Map<::djinni::String, ::djinni::Set<::djinni::String>>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOptionalSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableOptionalSet.cpp b/test-suite/generated-src/jni/NativeParcelableOptionalSet.cpp
index 1cd833a4b..97618e829 100644
--- a/test-suite/generated-src/jni/NativeParcelableOptionalSet.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableOptionalSet.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableOptionalSet::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableOptionalSet>::get();
-    return {::djinni::Optional<std::experimental::optional, ::djinni::Set<::djinni::String>>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOptionalSet))};
+    return {::djinni::Optional<std::experimental::optional, ::djinni::Set<::djinni::String>>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOptionalSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelablePrimitives.cpp b/test-suite/generated-src/jni/NativeParcelablePrimitives.cpp
index c548dbb7f..11c084b27 100644
--- a/test-suite/generated-src/jni/NativeParcelablePrimitives.cpp
+++ b/test-suite/generated-src/jni/NativeParcelablePrimitives.cpp
@@ -39,24 +39,24 @@ auto NativeParcelablePrimitives::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 19);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelablePrimitives>::get();
-    return {::djinni::Bool::toCpp(jniEnv, jniEnv->GetBooleanField(j, data.field_mB)),
-            ::djinni::I8::toCpp(jniEnv, jniEnv->GetByteField(j, data.field_mEight)),
-            ::djinni::I16::toCpp(jniEnv, jniEnv->GetShortField(j, data.field_mSixteen)),
-            ::djinni::I32::toCpp(jniEnv, jniEnv->GetIntField(j, data.field_mThirtytwo)),
-            ::djinni::I64::toCpp(jniEnv, jniEnv->GetLongField(j, data.field_mSixtyfour)),
-            ::djinni::F32::toCpp(jniEnv, jniEnv->GetFloatField(j, data.field_mFthirtytwo)),
-            ::djinni::F64::toCpp(jniEnv, jniEnv->GetDoubleField(j, data.field_mFsixtyfour)),
-            ::djinni::String::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mS)),
-            ::djinni::Date::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mD)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::Bool>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOB)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I8>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOEight)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I16>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOSixteen)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOThirtytwo)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::I64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOSixtyfour)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::F32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOFthirtytwo)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::F64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOFsixtyfour)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::String>::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mOS)),
-            ::djinni::Optional<std::experimental::optional, ::djinni::Date>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mOD))};
+    return {::djinni::Bool::toCpp(jniEnv, (jniEnv->GetBooleanField(j, data.field_mB))),
+            ::djinni::I8::toCpp(jniEnv, (jniEnv->GetByteField(j, data.field_mEight))),
+            ::djinni::I16::toCpp(jniEnv, (jniEnv->GetShortField(j, data.field_mSixteen))),
+            ::djinni::I32::toCpp(jniEnv, (jniEnv->GetIntField(j, data.field_mThirtytwo))),
+            ::djinni::I64::toCpp(jniEnv, (jniEnv->GetLongField(j, data.field_mSixtyfour))),
+            ::djinni::F32::toCpp(jniEnv, (jniEnv->GetFloatField(j, data.field_mFthirtytwo))),
+            ::djinni::F64::toCpp(jniEnv, (jniEnv->GetDoubleField(j, data.field_mFsixtyfour))),
+            ::djinni::String::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mS))),
+            ::djinni::Date::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mD))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::Bool>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOB))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I8>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOEight))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I16>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOSixteen))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOThirtytwo))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::I64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOSixtyfour))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::F32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOFthirtytwo))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::F64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOFsixtyfour))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::String>::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mOS))),
+            ::djinni::Optional<std::experimental::optional, ::djinni::Date>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mOD)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeParcelableSet.cpp b/test-suite/generated-src/jni/NativeParcelableSet.cpp
index 6e994adef..ee42c0f4f 100644
--- a/test-suite/generated-src/jni/NativeParcelableSet.cpp
+++ b/test-suite/generated-src/jni/NativeParcelableSet.cpp
@@ -22,7 +22,7 @@ auto NativeParcelableSet::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeParcelableSet>::get();
-    return {::djinni::Set<::djinni::String>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mSet))};
+    return {::djinni::Set<::djinni::String>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mSet)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativePrimitiveList.cpp b/test-suite/generated-src/jni/NativePrimitiveList.cpp
index f054e195f..137548b88 100644
--- a/test-suite/generated-src/jni/NativePrimitiveList.cpp
+++ b/test-suite/generated-src/jni/NativePrimitiveList.cpp
@@ -22,7 +22,7 @@ auto NativePrimitiveList::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativePrimitiveList>::get();
-    return {::djinni::List<::djinni::I64>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mList))};
+    return {::djinni::List<::djinni::I64>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mList)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeRecordUsingExtendedRecord.cpp b/test-suite/generated-src/jni/NativeRecordUsingExtendedRecord.cpp
index 05713778b..d3631f866 100644
--- a/test-suite/generated-src/jni/NativeRecordUsingExtendedRecord.cpp
+++ b/test-suite/generated-src/jni/NativeRecordUsingExtendedRecord.cpp
@@ -22,7 +22,7 @@ auto NativeRecordUsingExtendedRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppTyp
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeRecordUsingExtendedRecord>::get();
-    return {::djinni_generated::NativeExtendedRecord::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mEr))};
+    return {::djinni_generated::NativeExtendedRecord::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mEr)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeRecordWithDerivings.cpp b/test-suite/generated-src/jni/NativeRecordWithDerivings.cpp
index 707e7e364..6f3bb75b8 100644
--- a/test-suite/generated-src/jni/NativeRecordWithDerivings.cpp
+++ b/test-suite/generated-src/jni/NativeRecordWithDerivings.cpp
@@ -29,14 +29,14 @@ auto NativeRecordWithDerivings::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 9);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeRecordWithDerivings>::get();
-    return {::djinni::I8::toCpp(jniEnv, jniEnv->GetByteField(j, data.field_mEight)),
-            ::djinni::I16::toCpp(jniEnv, jniEnv->GetShortField(j, data.field_mSixteen)),
-            ::djinni::I32::toCpp(jniEnv, jniEnv->GetIntField(j, data.field_mThirtytwo)),
-            ::djinni::I64::toCpp(jniEnv, jniEnv->GetLongField(j, data.field_mSixtyfour)),
-            ::djinni::F32::toCpp(jniEnv, jniEnv->GetFloatField(j, data.field_mFthirtytwo)),
-            ::djinni::F64::toCpp(jniEnv, jniEnv->GetDoubleField(j, data.field_mFsixtyfour)),
-            ::djinni::Date::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mD)),
-            ::djinni::String::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mS))};
+    return {::djinni::I8::toCpp(jniEnv, (jniEnv->GetByteField(j, data.field_mEight))),
+            ::djinni::I16::toCpp(jniEnv, (jniEnv->GetShortField(j, data.field_mSixteen))),
+            ::djinni::I32::toCpp(jniEnv, (jniEnv->GetIntField(j, data.field_mThirtytwo))),
+            ::djinni::I64::toCpp(jniEnv, (jniEnv->GetLongField(j, data.field_mSixtyfour))),
+            ::djinni::F32::toCpp(jniEnv, (jniEnv->GetFloatField(j, data.field_mFthirtytwo))),
+            ::djinni::F64::toCpp(jniEnv, (jniEnv->GetDoubleField(j, data.field_mFsixtyfour))),
+            ::djinni::Date::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mD))),
+            ::djinni::String::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mS)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeRecordWithDurationAndDerivings.cpp b/test-suite/generated-src/jni/NativeRecordWithDurationAndDerivings.cpp
index de3d59023..3ec9f7390 100644
--- a/test-suite/generated-src/jni/NativeRecordWithDurationAndDerivings.cpp
+++ b/test-suite/generated-src/jni/NativeRecordWithDurationAndDerivings.cpp
@@ -23,7 +23,7 @@ auto NativeRecordWithDurationAndDerivings::toCpp(JNIEnv* jniEnv, JniType j) -> C
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeRecordWithDurationAndDerivings>::get();
-    return {::djinni::Duration<::djinni::F64, ::djinni::Duration_ns>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mDt))};
+    return {::djinni::Duration<::djinni::F64, ::djinni::Duration_ns>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mDt)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeRecordWithFlags.cpp b/test-suite/generated-src/jni/NativeRecordWithFlags.cpp
index 840ddde03..4cca5727c 100644
--- a/test-suite/generated-src/jni/NativeRecordWithFlags.cpp
+++ b/test-suite/generated-src/jni/NativeRecordWithFlags.cpp
@@ -22,7 +22,7 @@ auto NativeRecordWithFlags::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeRecordWithFlags>::get();
-    return {::djinni_generated::NativeAccessFlags::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mAccess))};
+    return {::djinni_generated::NativeAccessFlags::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mAccess)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeRecordWithNestedDerivings.cpp b/test-suite/generated-src/jni/NativeRecordWithNestedDerivings.cpp
index 79bcae165..35d7393f6 100644
--- a/test-suite/generated-src/jni/NativeRecordWithNestedDerivings.cpp
+++ b/test-suite/generated-src/jni/NativeRecordWithNestedDerivings.cpp
@@ -24,8 +24,8 @@ auto NativeRecordWithNestedDerivings::toCpp(JNIEnv* jniEnv, JniType j) -> CppTyp
     ::djinni::JniLocalScope jscope(jniEnv, 3);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeRecordWithNestedDerivings>::get();
-    return {::djinni::I32::toCpp(jniEnv, jniEnv->GetIntField(j, data.field_mKey)),
-            ::djinni_generated::NativeRecordWithDerivings::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mRec))};
+    return {::djinni::I32::toCpp(jniEnv, (jniEnv->GetIntField(j, data.field_mKey))),
+            ::djinni_generated::NativeRecordWithDerivings::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mRec)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeSetRecord.cpp b/test-suite/generated-src/jni/NativeSetRecord.cpp
index 4ead65146..51b9925f9 100644
--- a/test-suite/generated-src/jni/NativeSetRecord.cpp
+++ b/test-suite/generated-src/jni/NativeSetRecord.cpp
@@ -23,8 +23,8 @@ auto NativeSetRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 3);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeSetRecord>::get();
-    return {::djinni::Set<::djinni::String>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mSet)),
-            ::djinni::Set<::djinni::I32>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mIset))};
+    return {::djinni::Set<::djinni::String>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mSet))),
+            ::djinni::Set<::djinni::I32>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mIset)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeTestOptionalExternInterfaceRecord.cpp b/test-suite/generated-src/jni/NativeTestOptionalExternInterfaceRecord.cpp
index a99af3bd0..5dfa42246 100644
--- a/test-suite/generated-src/jni/NativeTestOptionalExternInterfaceRecord.cpp
+++ b/test-suite/generated-src/jni/NativeTestOptionalExternInterfaceRecord.cpp
@@ -23,7 +23,7 @@ auto NativeTestOptionalExternInterfaceRecord::toCpp(JNIEnv* jniEnv, JniType j) -
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeTestOptionalExternInterfaceRecord>::get();
-    return {::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeSampleInterface>::toCpp(jniEnv, jniEnv->GetObjectField(j, data.field_mSampleInterface))};
+    return {::djinni::Optional<std::experimental::optional, ::djinni_generated::NativeSampleInterface>::toCpp(jniEnv, (jniEnv->GetObjectField(j, data.field_mSampleInterface)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeUserToken.cpp b/test-suite/generated-src/jni/NativeUserToken.cpp
index a1bc87eb5..656c219f4 100644
--- a/test-suite/generated-src/jni/NativeUserToken.cpp
+++ b/test-suite/generated-src/jni/NativeUserToken.cpp
@@ -18,7 +18,7 @@ std::string NativeUserToken::JavaProxy::whoami() {
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeUserToken>::get();
-    auto jret = (jstring)jniEnv->CallObjectMethod(Handle::get().get(), data.method_whoami);
+    auto jret = reinterpret_cast<jstring>(jniEnv->CallObjectMethod(Handle::get().get(), data.method_whoami));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni::String::toCpp(jniEnv, jret);
 }
diff --git a/test-suite/generated-src/jni/NativeUsesSingleLanguageListeners.cpp b/test-suite/generated-src/jni/NativeUsesSingleLanguageListeners.cpp
index dd909ac1b..e241d76e6 100644
--- a/test-suite/generated-src/jni/NativeUsesSingleLanguageListeners.cpp
+++ b/test-suite/generated-src/jni/NativeUsesSingleLanguageListeners.cpp
@@ -27,7 +27,7 @@ std::shared_ptr<::testsuite::ObjcOnlyListener> NativeUsesSingleLanguageListeners
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeUsesSingleLanguageListeners>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnForObjC);
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnForObjC));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni_generated::NativeObjcOnlyListener::toCpp(jniEnv, jret);
 }
@@ -43,7 +43,7 @@ std::shared_ptr<::testsuite::JavaOnlyListener> NativeUsesSingleLanguageListeners
     auto jniEnv = ::djinni::jniGetThreadEnv();
     ::djinni::JniLocalScope jscope(jniEnv, 10);
     const auto& data = ::djinni::JniClass<::djinni_generated::NativeUsesSingleLanguageListeners>::get();
-    auto jret = jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnForJava);
+    auto jret = (jniEnv->CallObjectMethod(Handle::get().get(), data.method_returnForJava));
     ::djinni::jniExceptionCheck(jniEnv);
     return ::djinni_generated::NativeJavaOnlyListener::toCpp(jniEnv, jret);
 }
diff --git a/test-suite/generated-src/jni/NativeVarnameRecord.cpp b/test-suite/generated-src/jni/NativeVarnameRecord.cpp
index 4d3e34293..54716851f 100644
--- a/test-suite/generated-src/jni/NativeVarnameRecord.cpp
+++ b/test-suite/generated-src/jni/NativeVarnameRecord.cpp
@@ -22,7 +22,7 @@ auto NativeVarnameRecord::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeVarnameRecord>::get();
-    return {::djinni::I8::toCpp(jniEnv, jniEnv->GetByteField(j, data.field_mField))};
+    return {::djinni::I8::toCpp(jniEnv, (jniEnv->GetByteField(j, data.field_mField)))};
 }
 
 }  // namespace djinni_generated
diff --git a/test-suite/generated-src/jni/NativeWcharTestRec.cpp b/test-suite/generated-src/jni/NativeWcharTestRec.cpp
index ee981e5b2..91a47cfb3 100644
--- a/test-suite/generated-src/jni/NativeWcharTestRec.cpp
+++ b/test-suite/generated-src/jni/NativeWcharTestRec.cpp
@@ -22,7 +22,7 @@ auto NativeWcharTestRec::toCpp(JNIEnv* jniEnv, JniType j) -> CppType {
     ::djinni::JniLocalScope jscope(jniEnv, 2);
     assert(j != nullptr);
     const auto& data = ::djinni::JniClass<NativeWcharTestRec>::get();
-    return {::djinni::WString::toCpp(jniEnv, (jstring)jniEnv->GetObjectField(j, data.field_mS))};
+    return {::djinni::WString::toCpp(jniEnv, reinterpret_cast<jstring>(jniEnv->GetObjectField(j, data.field_mS)))};
 }
 
 }  // namespace djinni_generated